A semiconductor device such as a switching device or a diode is used in a circuit such as a switching power supply or an inverter. These semiconductor devices are required to have a high breakdown voltage and a low on-resistance. A relation between the breakdown voltage and the on-resistance is a trade-off relation depending on a semiconductor material used for the device.
Due to the progress of the technological development so far, a semiconductor device having a low on-resistance close to a limit of silicon has been realized. In order to further improve the breakdown voltage or further reduce the on-resistance, it is necessary to change the semiconductor material from silicon. It is possible to improve the trade-off relation depending on a material and to significantly increase the breakdown voltage and reduce the on-resistance by using a GaN-based semiconductor such as GaN or AlGaN, or a wide bandgap semiconductor such as silicon carbide (SiC) as the semiconductor material for switching device.
However, for example, in a switching device using the GaN-based semiconductor, a parasitic leakage path may be formed between electrodes due to a process peculiar to the GaN-based semiconductor and a leakage current of the device may be increased.